Exhaust wafts from a car tailpipe in this 2009 photo from Olympia, Washington. California, Washington and other states have adopted tailpipe emission rules stronger than the federal standard. Recent rhetoric from EPA Administrator Scott Pruitt has heightened fears the Trump administration may seek to block those states from implementing their standards. Steve BloomThe Olympian

Exhaust wafts from a car tailpipe in this 2009 photo from Olympia, Washington. California, Washington and other states have adopted tailpipe emission rules stronger than the federal standard. Recent rhetoric from EPA Administrator Scott Pruitt has heightened fears the Trump administration may seek to block those states from implementing their standards. Steve BloomThe Olympian

Is Trump’s EPA chief bluffing? Or will he gut California’s tough emissions standards?

California officials and clean air advocates are increasingly concerned the Trump administration may attempt to unravel a key program to drive down greenhouse gas emissions from automobile fleets while also jeopardizing the ability of California and other states to set pollution standards stronger than federal rules.

Backed by automakers, Trump officials are in talks with their California counterparts to weaken tough vehicle tailpipe standards approved by the Obama administration. The standards are aimed at reducing greenhouse gases, but could also help reduce emissions that cause smog and particulate pollution, and 13 other states have adopted them, including Washington, Pennsylvania and New York.

California has long enjoyed the authority to set pollution standards stronger than the federal government’s, a legacy of the state’s early battles against urban smog, which predated the 1970 Clean Air Act. But in testimony to a Senate committee last week, U.S. Environmental Protection Agency Administrator Scott Pruitt left open the possibilty he might seek to revoke California’s authority.

Never miss a local story.

Three days after Pruitt’s comments, the chair of the California Air Resources Board issued her own warning shot against possible EPA intervention.

“I think there would be a war with many states lining up with California,” said CARB Chairwoman Mary Nichols, speaking at a Palo Alto conference sponsored by Bloomberg New Energy Finance.

Nichols and other state officials note that the EPA, under the Obama administration, granted California a 2013 waiver to implement its own, tougher tailpipe standards. Never before has an EPA administrator attempted to revoke a waiver previously granted to the state.

“The EPA would have to take unprecedented legal action to try to revoke that waiver,” Nichols said during the Feb. 2 conference. “Our best legal judgment is that that can’t be done.”

I think there would be a war with many states lining up with California

Mary Nichols, chairwoman of the California Air Resources Board

Trump’s latest spat with California and other states comes as the president works to shore up his support among the auto industry in Detroit and Michigan, a state he won, to the surprise of Democrats, in 2016. Since then, Trump has kept his focus on Michigan, pledging in his State of the Union address to cut government mandates and “get the Motor City revving its engines.”

The U.S. auto industry has long opposed conflicting state and federal standards for tailpipe emissions and fuel economy. Auto manufacturers say such conflicts force them to design and make different versions of the same vehicle, driving up prices.

When the Obama administration was in office, it struck a grand bargain with California and automakers to raise the average fuel economy of new cars and light trucks to more than 50 miles per gallon by 2025, as a way to reduce carbon dioxide emissions. The deal, however, included a “midterm review” in 2018 to determine if the final requirements were feasible.

Before leaving office, the Obama administration kept the final requirements in place, over protests of the auto industry. In August, Pruitt and the Transportation Department officially announced they were reviewing and possibly rewriting those standards, which would affect the 2022-2025 model years.

The Trump administration’s plans will be known soon. The EPA plans to decide on future tailpipe emission standards by April 1, and the National Highway Traffic Safety Administration will reveal its new federal fuel economy standards for cars and light trucks by March 30.

Even if Trump revises the Obama-era rules, California and other states could still implement its tougher restrictions, a prospect that concerns many automakers.

“For us, one national program is very important,” said Gloria Bergquist, Vice President for Communication at the Alliance of Auto Manufacturers in Washington, D.C. “It’s good for consumers, and it avoids duplicative programs with duplicative costs.”

In December, several federal officials met with the California Air Resources Board in Sacramento to discuss a possible national standard. The meeting, first reported by Reuters, included William Wehrum, who leads the EPA's Office of Air and Radiation, National Highway Traffic Safety Administration deputy chief Heidi King, and Mike Catanzaro, a senior White House aide.

Asked about the status of talks, an EPA spokesman directed McClatchy to Wehrum’s recent comments to reporters, saying he had held “productive discussions” with CARB. Wehrum added he “had no interest whatsoever in withdrawing California’s ability to regulate,” a comment that provoked some laughs back in California.

When Wehrum served in the EPA during the George W. Bush administration, he was a key figure in rejecting California’s original request for a waiver to reduce greenhouse gases from automobiles. California sued over that decision, which was ultimately reversed when Obama came to office.

The potential for California to strike a deal with the Trump administration concerns some environmentalists, but they doubt it will happen. “I’m not sure that there is any room for compromise on California’s part,” said Irene Gutierrez, a San Francisco-based lawyer with the Natural Resources Defense Council, a leading environmental group. CARB officials did not respond to an inquiry.

Gutierrez said California has spent years documenting how its standards are feasible and crucial to the state’s goals of reducing greenhouse gases. California law requires it to cut carbon dioxide emissions to 40 percent below 1990 levels by 2030.

A big part of that program is transitioning to electric and other zero-emission vehicles. At his recent State of the State speech, Gov. Jerry Brown unveiled plans to have 5 million zero-emission vehicles in California by 2030, up from a planned 1.5 million in 2025.

California showed further defiance toward the Trump EPA on Thursday. The California Air Resource Board voted to retain two Obama-era rules on greenhouse gas emissions from medium-and-heavy duty trucks, after the EPA claimed it lacked the authority to enact the rules.

If EPA’s Pruitt sought to revoke California’s tailpipe emissions waiver, he would likely unravel the peace treaty struck under Obama, which halted years of litigation involving California, the auto industry and other players. EPA would have to go through a rulemaking process to revoke the waiver, which could take years, and then prevail in expected litigation.

Jasper Sheriff turned on his blue lights for Christmas cars, but not for a ticket

Ted Turner's private Beaufort County island is for sale. Here's what you get

Three years of research by nearly 100 health and science experts predicts that thousands will die or get sick because of the impacts associated to climate change. Dr. John P. Holdren, assistant to the President for Science and Technology, and Gina McCarthy, administrator of the Environmental Protection Agency (EPA) outlined the new scientific assessments regarding increased deaths and hospitalizations due to more air pollution, extreme heat and severe weather brought on by climate change. The White House